The goal of this pilot study is to determine the therapeutic efficacy and safety of the vitamin D analog 19-nor-1 alfa, 25-dihydroxyvitamin D3 for the treatment of plague type psoriasis in adults. This will be accomplished by evaluating the topical application of either placebo petrolatum or petrolatum that contains 1.5 mcg of 19-nor-1,25(OH)2D3 in 0.1 g petrolatum. Expected outcome: Only 19-nor-1,25 (OH)2D3 will be effective for treating psoriasis. A total of up to 20 adults patients with plague psoriasis who have lesions over at least 5% of their bodies will be studied. Study subjects will be male or female between the ages of 18-80. The patients will apply to a 50 cm2 lesion 0.10g of white petrolatum that contains 1.5 mcg of 19-nor-1,25 (OH)2D3 once a day for three months. A comparable 50 cm2 psoriasis lesion will receive 15 mcg/g of white petrolatum daily. The study will be conducted in a double blind, right/left sided, semi-controlled fashion. Neither the physician nor study nurse who is making the assessment will know which lesion is receiving which compound.